<meta charset="utf-8">
(#) Prefer List over Array

!!! WARNING: Prefer List over Array
   This is a warning.

Id
:   `MoshiUsageArray`
Summary
:   Prefer List over Array
Severity
:   Warning
Category
:   Correctness
Platform
:   Any
Vendor
:   slack
Identifier
:   slack-lint
Contact
:   https://github.com/slackhq/slack-lints
Feedback
:   https://github.com/slackhq/slack-lints
Min
:   Lint 8.7+
Compiled
:   Lint 8.7+
Artifact
:   [com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.md.html)
Since
:   0.1.0
Affects
:   Kotlin and Java files and test sources
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/main/java/slack/lint/MoshiUsageDetector.kt)
Tests
:   [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/MoshiUsageDetectorTest.kt)
Copyright Year
:   2021

Array types are not supported by Moshi, please use a List instead.
Arrays are expensive to manage in JSON as we don't know lengths ahead of
time and they are a mutable code smell in what should be immutable value
classes. Otherwise, moshi-gson-interop will hand serialization of this
property to Gson, which may or may not handle it. This will eventually
become an error after GSON is removed.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/slack/model/Example.kt:43:Warning: Prefer List over Array.
[MoshiUsageArray]
  val arrayType: Array&lt;String&gt;,
                 -------------
src/slack/model/Example.kt:44:Warning: Prefer List over Array.
[MoshiUsageArray]
  val intArray: IntArray,
                --------
src/slack/model/Example.kt:45:Warning: Prefer List over Array.
[MoshiUsageArray]
  val boolArray: BooleanArray,
                 ------------
src/slack/model/Example.kt:46:Warning: Prefer List over Array.
[MoshiUsageArray]
  val complexArray: Array&lt;List&lt;String&gt;&gt;,
                    -------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here are the relevant source files:

`src/external/ExternalType.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package external

class ExternalType
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`src/external/ExternalTypeAnnotated.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package external

import com.squareup.moshi.JsonClass

@JsonClass(generateAdapter = true)
data class ExternalTypeAnnotated(val value: String)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`src/slack/model/Example.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package slack.model

import androidx.annotation.Keep
import com.squareup.moshi.JsonAdapter
import com.squareup.moshi.JsonClass
import java.util.ArrayList
import java.util.HashSet
import java.util.HashMap
import java.util.Date
import external.ExternalType
import external.ExternalTypeAnnotated
import slack.InternalType
import slack.InternalTypeAnnotated
import slack.InternalTypeAnnotated2
import dev.zacsweers.moshix.adapters.AdaptedBy
import test.CustomQualifier

@JsonClass(generateAdapter = true)
data class Example(
  // collections
  val okList: List<Int>,
  val okSet: Set<Int>,
  val okCollection: Collection<Int>,
  val okMap: Map<String, String>,
  val concreteList: ArrayList<Int>,
  val concreteSet: HashSet<Int>,
  val concreteMap: HashMap<String, String>,
  // platform
  val platformType: Date,
  @AdaptedBy(DateFactory::class) val adaptedByOk: Date,
  // external
  val externalType: ExternalType,
  val externalTypeAnnotated: ExternalTypeAnnotated,
  // internal
  val internalType: InternalType,
  val internalTypeAnnotated: InternalTypeAnnotated,
  val internalTypeAnnotated2: InternalTypeAnnotated2,
  val int: Int,
  val string: String,
  val nullableString: String?,
  val any: Any,
  // Arrays
  val arrayType: Array<String>,
  val intArray: IntArray,
  val boolArray: BooleanArray,
  val complexArray: Array<List<String>>,
  val badGeneric: List<ExternalType>,
  val badGeneric2: CustomGenericType<ExternalType>,
  val badNestedGeneric: CustomGenericType<List<ExternalType>>,
  // This would normally error but since it has a custom qualifier we skip the check
  @CustomQualifier val customQualifier: Date,
  // Mutable collections
  val mutableList: MutableList<Int>,
  val mutableSet: MutableSet<Int>,
  val mutableCollection: MutableCollection<Int>,
  val mutableMap: MutableMap<String, String>
)

@Keep
abstract class DateFactory : JsonAdapter.Factory

@JsonClass(generateAdapter = true)
data class CustomGenericType<T>(val value: T)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/MoshiUsageDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `MoshiUsageDetector.propertyTypes`.
To report a problem with this extracted sample, visit
https://github.com/slackhq/slack-lints.

(##) Including

!!!
   This is not a built-in check. To include it, add the below dependency
   to your project. This lint check is included in the lint documentation,
   but the Android team may or may not agree with its recommendations.

```
// build.gradle.kts
lintChecks("com.slack.lint:slack-lint-checks:0.8.2")

// build.gradle
lintChecks 'com.slack.lint:slack-lint-checks:0.8.2'

// build.gradle.kts with version catalogs:
lintChecks(libs.slack.lint.checks)

# libs.versions.toml
[versions]
slack-lint-checks = "0.8.2"
[libraries]
# For clarity and text wrapping purposes the following declaration is
# shown split up across lines, but in TOML it needs to be on a single
# line (see https://github.com/toml-lang/toml/issues/516) so adjust
# when pasting into libs.versions.toml:
slack-lint-checks = {
    module = "com.slack.lint:slack-lint-checks",
    version.ref = "slack-lint-checks"
}
```

0.8.2 is the version this documentation was generated from;
there may be newer versions available.

[Additional details about com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.md.html).
(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("MoshiUsageArray")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("MoshiUsageArray")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection MoshiUsageArray
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="MoshiUsageArray" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'MoshiUsageArray'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore MoshiUsageArray ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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